Bioactive silicate glasses have found application for forming scaffolds for repairing human tissue. These glasses are advantageous in such applications in view of their biodegradability, biocompatibility, and ability to form a chemically strong bond to living bone.
But because of the inherent brittleness and low tensile strength of bioactive silicate glasses, such as the well known 45S5 glass, the commercial use of bioactive glasses is currently limited to non-load bearing bone sites. A main reason why bioactive glasses are not being used to repair load-bearing bones is their low mechanical strength and brittle failure characteristics, particularly when subjected to tensile and flexural (bending) stresses. While glass has a high compressive strength, it is much weaker when subjected to tensile/bending stresses. The loading conditions that a bioactive glass scaffold might encounter at a load-bearing bone site (e.g., the repair of a broken femur in the leg) can be quite variable, ranging from compressive stresses to tensile and bending stresses. Glass being a brittle material may fail catastrophically under such conditions and this limits its use in the body where it might be subjected to tensile/bending stresses.